Reduce logic in Pipelines Vue mixin

What does this MR do?

Depends on: !53833 (merged)

This MR removes a Vue mixin that is used in the Pipelines Tables. The idea is to reduce the amunt of moving parts in our implementation by gradually removing mixin logic.

• Deleted a mixin by moving methods that can be moved out of Vue mixin to full the Vue component and/or the "sibling" Vue mixin.
• Moves component registrations out of the resulting mixin to have a clean import path: #301015 (closed)

Screenshots (strongly suggested)

N/A

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team